U.S. Army Multiball Cartridge R&D Redux, 2018

What goes around comes around, the military multiball cartridge research & development returns again: U.S. Army Multiball R&D 2018.pdf (1.0 MB)



Brian, thanks for sharing this one!

Let’s see what happens when one of the young designers gets a booklet on squeeze bores in his hands…

Many things are getting re-invented rather than invented…
And guns and ammunition are a very good example for this. I guess if one would make a list of all these things it would be rather long.

Why wouldn’t a a M240 loaded with duplex be effective?

Was it with the M60 50 years back?


I heard the Remchester is working on a new combustible fiber-wrapped cartridge with a primer that ejects separately, shortening the extraction cycle. ;)

Is that a Gerlich style???

No, it is inside a sabot.

M198 was not as successful as hoped. As an example, report “Accuracy of Rifle Fire: SPIW, M16A1, M14” can be downloaded from dtic.mil as AD390136

Thank you for the clarification!

I believe that relative cost was the ultimate prohibitive factor in getting this sort of munition mainstreamed into service. Not that the Pentagon isn’t legendary for sporadic wasteful spending, but they are equally sporadic with their stinginess.

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DK is correct with his first sentence, but his comments in the second are a bit more complex. Congress approves what the services spend by individual line item. They have been known to require USAF buy additional F-111s that were then parked because they then refused to fund the spare parts required to fly them as well as the pilots, maintenance crew, etc. There are lots of wasteful spending. Once upon a time I authorized the repair of f-15 & F-15 engine parts that cost almost twice as much to repair as a new part cost because Sen John Glenn had reduced the spare parts buy so that there was no money to buy new items, but there was money to repair which came from a different funding pot, but required we defer the repair of other less critical items. Is the Pentagon and the services blameless, No, but the rules/laws on the budget and financial control create an incredibly clumsy system where there are few good alternatives.

Enough of the soapbox!!!

A good example his first sentence occured about 25 years aboat Eglin AFB, the USAF development center for munitions. At the request of the combat commends Eglin designed a new family of 20mm projectiles for the Vulcan cannon on the F-15 & F-16 fighters. The redesigned projectiles had considerably less drag and therefore reduced flight time to the target which significantly improved both the air-to-air and air-to-ground engagement effectiveness The terminal effects/lethality of the projectiles were also improved.

The problem was that we still had sufficient 20mm rounds of the old design to fight a world war in the 1980s and this was the early 1990s and the cold war was over and we had more 20mm Vulcan ammo than we would ever use. despite of the very significant improvement in capability and wartime performance, The cost of replacing the stockpile was too high so this new “High Performance 20mm Ammo” was shelved and still, as far as I know has never been acquired!

This situation occurs often with munitions where wartime quantities are acquired and stored. New acquisitions are often limited to those cases where there is no capability with existing weapons. Simple improved performance is difficult to find money to acquire.


Lew, it seems you are speaking of the PGU series ammo then.
Today it is in service. I assume those giant stocks of the old M50 type you mentioned simply expired and had to be replaced at one point.

The ammo:

The engineer that presented the paper on multiplex ammunition said this was just a research project, no driver to develop any new ammunition along these lines. And yes, he was quite familiar with the Salvo Squeezebore rounds, not to mention the 7.62 duplex, SPIW, flechette shotshells, Advanced Combat Rifle rounds, etc. We had quite a discussion on the topic at NDIA and after.

I find this quite interesting from the standpoint of my being involved in the U.S. Agriculture Research Service (ARS, U.S. Dept. of Agriculture) where all research projects have extensive ARS “in house” oversight and Congressional oversight, must have a specified goal and must be “customer oriented” (a rather nebulous term).

Doing a research project for the sake of “basic research” has long since fallen by the wayside. At least in my experience.


Great to see it in production. The PGU series of ammo was designed in the late 1982 and completed testing in the early 1990s so the design is about 30 years old!!!

I wonder is new 20mm are in the design phase for the USAF???


Lew, what means “design phase for the USAF”?

The Frangible Armor Piercing (FAP) rounds look very interesting.


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Development goes through three phases, concept development which is funded with one type of R&D funds (6.2), and full scale development (6.3) funds which is detail design of the item, prototype fabrication and testing and design of the production item. Out of full scale development comes a production decision and initial production which is another type of funds. The concept development started in 1989, though there was probably some concept studies earlier than that to define and justify concept development. Concept development was to be basically complete by late 1991. Some full scale development was to begin in 1991 and be completed by 1993.

Before concept development there is a period, involving the combat commands of defining the military requirement and considering technology to satisfy the requirement, and studies to initially quantify the benefits of a new development. This leads to a formally approved USAF defined requirement which must be done before 6.2 funds are allocated.

The names above were the ones in use when this development was ongoing. They have changed a couple of times since then.

This is the short version, the DOD directions, which is mostly based on Congressional legislation, and the USAF direction implementing this direction in the USAF is volumes.

If the round doesn’t have a PGU designation, then it wasn’t designed for the USAF or type designated by the USAF.


Lew, I almost got it now. :-)

Yes, these have PGU designations.

Here a General Dynamics flyer on them:
20mm-x-102-PGU-USAF.pdf (1.7 MB)


20mm MPT-SD (for the Air defense role)

25x137 for the F35

Wed15439Sande.pdf (2.4 MB)